From 73df97dcdc302fe520b8fdbd2d10d617ac3dd158 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Fri, 29 May 2026 00:09:27 +0100
Subject: [PATCH] Fix crash on deferred generic class nested in function

---
 mypy/semanal.py                      |  3 ++-
 test-data/unit/check-newsemanal.test | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/mypy/semanal.py b/mypy/semanal.py
index e3524f2c7db6..92f5c3d44333 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -1156,7 +1156,8 @@ def prepare_method_signature(self, func: FuncDef, info: TypeInfo, has_self_type:
                         leading_type = fill_typevars(info)
                     if func.is_class or func.name == "__new__":
                         leading_type = self.class_type(leading_type)
-                    func.type = replace_implicit_first_type(functype, leading_type)
+                    if not has_placeholder(leading_type):
+                        func.type = replace_implicit_first_type(functype, leading_type)
                 elif has_self_type and isinstance(func.unanalyzed_type, CallableType):
                     if not isinstance(get_proper_type(func.unanalyzed_type.arg_types[0]), AnyType):
                         if self.is_expected_self_type(
diff --git a/test-data/unit/check-newsemanal.test b/test-data/unit/check-newsemanal.test
index b0b01ad3a593..cfb59a9f8e9b 100644
--- a/test-data/unit/check-newsemanal.test
+++ b/test-data/unit/check-newsemanal.test
@@ -3228,3 +3228,16 @@ def deco(fn: Callable[[], T]) -> Callable[[], T]: ...
 
 @deco
 def defer() -> int: ...
+
+[case testNestedClassSelfNoPlaceholder]
+from typing import Generic, TypeVar
+
+def test() -> None:
+    T = TypeVar("T", bound="Model")
+
+    class Query(Generic[T]):
+        def filter(self, value: T) -> None:
+            ...
+
+    class Model:
+        pass